Process using shock waves for the continuous treatment of threads

ABSTRACT

This invention relates to a process for squeezing and/or drying a humid thread, particularly a textile thread, in the course of a treatment, such as dyeing, effected continuously on said thread during the rectilinear displacement thereof, wherein the humid thread is passed into a zone traversed by a current of air at a pressure much lower than the pressure prevailing about the thread during the operation having provoked it humidification. The invention also relates to an apparatus for continuously treating a thread, for example a textile thread, applying the process as described hereinabove.

Letebvre et al. 1 1 Apr. 3, 1973 541 PROtIESS USHNG SHOCK WAVES F02,194,565 3/1940 Moss ..34/16 x THE CGNTINUOUS TREATMENT OF 2,622,96112/1952 Finlayson et al ..68/D1G, 1 3,346,932 10/1967 Cheape, Jr..34/155 x THREADS Inventors: Michel S. M. Lefebvre, Saint- Quentin;Jean-Claude M. L. Hennion, Arly, both of France Assignee: Omnium DeProspective lndustrielle,

Saint-Quentin, France Filed: Jan. 111, 1971 Appl. No.: 107,166

Foreign Application Priority Data Jan. 21, 1970 France ..7002183 U.S.Cl. ..34/16, 34/23, 34/61 Int. Cl ..F26b 5/04 Field of Search ..34/l6,23, 61, 155, DIG. 14;

68/355, 20, DIG. 1; 28/61, 75; 117/102 L References Cited uNrrEn STATEPATENTS 4/1971 Heisler .....3 4/16x" Primary Examiner-William F. ODeaAssistant Examiner-William C. Anderson Attorney-Ward, McElhannons,Brooks & Fitzpatrick [57] ABSTRACT This invention relates to a processfor squeezing and/or drying a humid thread, particularly a textilethread, in the course of a treatment, such as dyeing, effectedcontinuously on said thread during the rectilinear displacement thereof,wherein the humid thread is passed into a zone traversed by a current ofair at a pressure much lower than the pressure prevailing about thethread during the operation having provoked it humidification. Theinvention also relates to an apparatus for continuously treating athread, for example a textile thread, applying the process as describedhereinabove.

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' appear successively in the course of dyeing a PROCESS USING SHOCKWAVES FOR THE CONTINUOUS TREATMENT OF THREADS The present inventionrelates to a process and apparatus for the continuous treatment ofthreads.

It is known that, after spinning, textile threads may undergo varioustreatments, for example dyeing or coating. At present, these treatmentsare effected on thread bobbins, and sometimes on skeins,but theirefficacity does not always present the desired homogeneity.

However, different processes are known for subjecting threads to certaintreatments during the continuous advance movement thereof. Suchcontinuous treatments generally consist in depositing a product on thethread to be treated, for example by passing this thread in a bath, thenin eliminating the excess of treating fluid by scraping obtained forexample by means of an air current circulating near the thread.

The continuous treatments of threads known up to the present day did notpermit a precise dosing of the quantity of the product deposited nor asuitable penetration of this product in the thread. This was due inparticular to the fact that the squeezing and possibly the drying of thethread by the air current were insufficient.

The invention firstly has for its object to remedy the above-mentioneddisadvantages and relates to a process for squeezing and/or drying ahumid thread, particularly a textile thread, utilizable in particularduring a treatment, such as dyeing, effected continuously on saidthread. According to the invention, the humid thread is passed through azone through which passes an air current at a pressure much lower thanthe pressure prevailing around the thread during the operation havingprovoked its humidification.

According to an advantageous embodiment of the invention, the lowpressure zone is created in the supersonic flow of an air current at theoutlet of a convergent-divergent nozzle through which the'thread passes.

Various other characteristics of this process and its execution willappear hereinafter in the course of the detailed description.

The invention also has for its object a particular application of theabove-defined process, particularly for the purpose of making dyed zonesand non-dyed zones thread.

According to this latter application, after coming from a dyeing bath,the thread is passed into two convergent-divergent nozzles, the secondof said nozzles being permanently fed by an air current whose pressureupstream of said nozzle is higher than the critical pressure at theconstriction of this nozzle, whilst the i first nozzle is fed by acurrent of air whose pressure upstream of said first nozzle isalternately higher then lower than the critical" pressure at theconstriction of this first nozzle.

Secondary characteristics of this particular application as well as itsadvantages will appear hereinafter, in the course of the detaileddescription.

Finally, the invention has for its object an apparatus enabling theabove-defined process and its particular application to be carried out,for the purpose of effecting on threads all types of treatments,particularly dyeing, which are continuously applied during a rectilineardisplacement of the thread. The present invention provides both aperfect homogeneity of the treated thread as well as high speed of thetreatment.

However, it should be noted that the invention may be applied to alltypes of natural or synthetic, textile or metallic threads. The wordthread as used herein means any supple element of very small diameterwith respect to its length.

The apparatus comprises at least two elementary treatment chambers, eachof them corresponding to a phase of the complete treatment that a threadmust undergo. These elementary treatment chambers are aligned and arecovery zone is provided therebetween for the active products used inthe elementary treatment chambers, at least in the first of them.

Each treatment chamber comprises two apertures for the inlet and outletof the thread, these two apertures being aligned with those of the othertreatment chambers in the direction of the thread and having a diameterclose to this latter. The shape of these apertures depends upon thenature of the treatment and will be specified later. On the other hand,there opens out into each treatment chamber a pipe connected to a sourceof treatment fluid.

According to the invention, the recovery zone for the treatment fluidsis shaped as a chamber which surrounds, in sealed manner, the outletaperture of one treatment chamber as well as the inlet aperture of thefollowing treatment chamber, whilst each treatment chamber fed with achemically active fluid is followed by a treatment chamber fed by aninert gas, such as compressed air. Of course, the recovery chambercomprises at least one pipe connected to a recovery tank for a treatmentfluid.

In fact, in practice, it is frequently advisable, particularly in thecase of textile threads, to repeatedly dose the thread by an activeagent. This is why, as has just been indicated, at least certain of thetreatment chambers ensure only squeezing and/or drying operations andare consequently fed by an inert gas and disposed after each treatmentchamber fed by an active fluid:

. dye, acid, etc.

The invention will moreover be more readily understood and itsadvantages as well as various secondary characteristics will appear inthe course of the following description of a few embodiments givensolely by way of example. To this end, reference will be made to theaccompanying drawings, in which:

FIG. 1 is a schematic view of a first apparatus according to theinvention.

FIG. 2 is a schematic view of a convergent-divergent nozzle equipping atleast certain of the treatment chambers fed by an inert gas.

FIG. 3 is a schematic view of a second apparatus according to theinvention, applicable in particular in the case of dyeing a textilethread.

FIG. 4, 5 and 6 show variants of the apparatus of FIG. 3 utilizable inparticular when it is desired to obtain threads having treated zonesalternating with nontreated zones.

The embodiment described with reference to FIG. 1 corresponds to theapplication to a thread of a known coating treatment. In particular, itenables the weight and the resistance to abrasion of a textile thread tobe increased and to be made suitable for use in a sewing machine.

Such a treatment comprises the following active elementary phases:

a. attack of the thread by an acid bath containing the coating to bedeposited on the thread;

b. neutralization of the deposit in order to obtain the precipitation ofthe coating molecules;

c. washing;

d. squeezing and drying.

Referring now to the drawings, it is seen that the apparatus permittingapplication of this treatment comprises, aligned along the path followedby the thread A, elementary treatment chambers l, 2, 3, 4, 5 and 6.

The chamber 1, corresponding to the attack by the acid bath comprises apipe la connected to a tank of acid solution, by means of a pump 11. Thetwo apertures lb and 1c of this chamber are capillary tubes whosediameter, function of that of the thread to be treated, is determined soas to avoid, or at least limit, the leaks of liquid by gravity or bydrive. The pump 11 maintains a constant level of liquid in the chamber1.

On either side of the treatment chamber 1 are disposed two recuperationchambers 7 and 8. They respectively surround, in sealed manner, theapertures lb and 1c and have pipes 7a and 8a ensuring the recovery ofthe leakage liquid which is returned the tank 10.

The treatment chambers 2, 4 and 6 correspond to intermediate squeezingand possibly drying phases. Their ends are of course also surrounded insealed manner by the recovery chambers 8, l4, 15, 16, 17 and 22. In thiscase, however, the treatment fluid is compressed air passed through amain pipe 9 and terminating at the pipes 2a, 4a, 6a belonging to each ofsaid chambers. It should be emphasized that the inlet and outletapertures of these chambers 2, 4 and 6 are each in the shape of aconvergent-divergent nozzle, referenced 2b and 20 for the chamber 2. Theconvergent-divergent nozzles of chambers 2,

and 6 are fed upstream by a pressure higher than or at least equal tothe critical pressure at the constriction of the nozzle. It will berecalled on this subject that critical pressure designates the pressureprevailing at the constriction of a nozzle and from which a supersonicflow is obtained in the divergent part of the nozzle, although the flowis subsonic in the convergent part thereof.

The nozzles used in the apparatus according to the invention arepreferably set out according to known methods, so that, when they exist,the shock waves provoked by the return of the air to a subsonic speedare located outside the divergent part and not, asv is frequently thecase, inside said latter.

FIG. 2 shows such a nozzle which may be disposed at each end of thechambers 2, 4 and 6, or at least at one of said ends, preferably at theoutlet end for the thread A. In this Figure, 50 designates the wall ofthe chamber, 51 the convergent part of the nozzle and 52 the divergentpart.

As mentioned above, the shock waves provoked by the return of the air toa subsonic speed appear at the end of the divergent part 52. They havebeen shown by a solid line and a broken line, the first shock waves 54being of course decompression waves. They develop along thesubstantially conical surface 54 and reflect on themselves at the apex55 of this surface 54. As is known, they then become decompression wavesdeveloping along the surface 56. When they have reached the zone wherethe constant pressure P prevails, they reflect on this zone at 57 inorder then to develop along surface 58 up to its apex'59. It is knownthat, when shock waves reflect on a constant pressure zone, they changenature, so that the surface 58 is delimited by compression waves.Similar phenomena continue beyond the apex 59 but it is not necessary todescribe them in order to understand the invention.

It may be said that there is, outside the divergent part 52, 'a zone 60delimited by a network of shock waves. It is known that the pressure pprevailing inside this zone 60 is much lower than the ambient pressureP, outside the nozzle.

When the humid thread A penetrates into zone 60, part of the liquidthat-it carries is instantaneously evaporated. This evaporation is dueto the fact that the pressure in the zone 60 is much lower than thatwhich existed around the thread during the preceding treatment whichprovoked its humidification.

An effect of squeezing and/or drying of the thread is thus obtained, theefficacity of which depends upon the output of air (quantity of air perunit time) passing through the zone 60. In fact, the quantity ofresidual humidity of the thread at the outlet of the zone 60 dependssolely upon the partial pressure of saturation of the liquid carried bythe thread in this zone. Consequently, the output of air must beregulated as a function of the desired quantity of residual humidity. Inother words, the output of air must be sufficient for evacuating thehumidity released in the zone 60 and thus to maintain a partialsaturation pressure therein which is sufficiently low for theevaporation to continue suitably.

It should be emphasized here that the squeezing and/or drying processwhich has just been described is carried out in the zone 60 whatever thedirection of displacement of the thread may be. Thus, in the embodimentshown in the Figure, this process may be carried out either at theinlet, or at the outlet of the chamber 2, 4 or 6, or at the two placessimultaneously. This will be of particular interest in the case ofcertain embodiments described later.

However, in the case where the thread penetrates into an inlet aperturesuch as 2b, there is added to the evaporation effect describedhereinbefore, a purely mechanical squeezing of the thread near theconstriction of the convergent-divergent nozzle. Thus, during thepassage of the thread in the inlet aperture 2b, the combination may beobtained of pneumatic effects which ensure both the complete penetrationof the thread by the acid solution brought during the passage into thechamber 1 and the'regulation of the amount of the thread in acidsolution, as well as the elimination by projection of the excess of acidsolution, which is then taken up by the recovery pipe 8a.

The treatment chamber 3 is similar to chamber 1 and is fed by aneutralizing bath coming from a tank 12 by means of a pump 13. It is thesame for the chamber 5 which is fed by a washing bath coming from a tankby means of a pump 21.

On the other hand, the treatment chambers 4 and 6 are similar to chamber2 and ensure, if necessary, an at least partial squeezing under theconditions that were explained above.

Finally, the pairs of recovery chambers 14-15 and 16-17 have the samecharacteristics and operate under the same conditions as the chambers7-8. They return the liquid recovered to tanks 18 and 19 respectivelysuitable for the recovery of the excess of liquid after neutralizationor after washing.

The last treatment chamber 6 may open out into the free air; however, incertain cases, it may be advantageous, as shown in the drawing, toensure a complete recovery of the air leaving this chamber. In fact, itmay be charged with solid, liquid or gaseous particles which would bedangerous to allow to escape into the atmosphere.

To this end, the outlet aperture 6b is prolonged by a recovery chamber22 whose recovery pipe 22a is inclined by about 45 on the axis of thethread. A conduit 22b connected to the main pipe 9 for compressed airopens out into the chamber 22 and directs the fluid leaving through theaperture 6b directly into the pipe 220.

It is obvious that, for certain treatments, an arrangement, similar tothat of chambers 6-22 may be provided for other pairs of treatment andrecovery chambers.

Finally, if it is considered necessary, a drying by heating may beprovided, either as an intermediate phase or as a final phase. As shownin the drawing, the thread passes through a capillary tube 23 surroundedby an isolating means in which a heating resistor 24 is embedded.

The above-described treatment may also take the form of a pure andsimple attack of a polyamide thread by hydrochloric acid, thedissolution of a part of the polyamide being outside the thread formingthe dissolution, the later treatment giving the effect of coagulationand leading to a final result of the same order as before. Such atreatment no longer necessitates any addition of polyamide on the outersurface of the thread.

Referring now to FIG. 3, an embodiment of the invention is shown whichis applicable more particularly to the dyeing of threads. In this case,as has already been indicated above, it is essential suitably to dosethe active product, in the present case the dye, and to be sure of thereproduceability of the modes of operation. The invention enables theseconditions to be easily fulfilled.

The apparatus comprises a first treatment chamber 31 provided with afeed pipe 31a connected to a dye tank 40 and equipped with a pump 41.This treatment chamber comprises inlet and outlet apertures for thethread, constituted by capillary tubes 31b and 310 opening out into therecovery chambers 37 and 38, which surround, in sealed manner, the endsof said tubes. Pipes 37a, 38a ensure the return of the excess .dye-tothe tank 40. Moreover, it is judicious to provide in the treatmentchamber itself a pipe 31d also connected to the tank 40 to maintain asubstantially constant level of the dyeing liquid to be maintained inthe chamber 31.

A second treatment chamber 32 is fed with compressed air guided througha pipe 32a. Of course, as has already been indicated, the inlet andoutlet apertures of the thread 32b and 320 are constituted byconvergentdivergent nozzles, preferably of the type such as thosedescribed hereinabove with reference to FIG. 2. In practice, it does notseem necessary to provide a recovery chamber at the outlet of thechamber 32 but such a recovery chamber may prove useful in certainparticular cases.

Similarly, a heating element similar to that described with reference toFIG. I may be disposed at the outlet of the chamber 32.

It should also be emphasized that the chamber 31 may be equipped withheating means, constituted for example by electrical resistors disposedinside the chamber or surrounding this latter. Tubes may also be usedthrough which passes a heating fluid, such as vapor, such tubes beingdisposable inside or outside the chamber 31. Similarly, the chamber 31may be disposed inside an enclosure heated by any suitable means.

Such heating means will be useful where the solubility of the dyeproducts should be increased or if it is necessary for the thread toundergo treatments such as bleaching and the application of finishes orthose which modify the tinctorial affinity.

The functioning of such an apparatus is similar to that which wasdescribed above, but it seems useful to emphasize a few particularpoints.

In the same way as before, P will designate the pressure of the air inthe pipe 32a and consequently in the chamber 32, and P and P the airpressures at the outlet of the aperture 32c and in the chamber 38respectively.

As soon as it enters in the aperture 32b, the thread A which brings withit a certain quantity of active agent, for example the dye liquidcontained in the chamber 31, meets a flow of gas which, as a function ofthe ratio P /P may be subsonic, sonic or supersonic. As explainedhereinabove, there may also be, near the aperture b, a combination ofpneumatic effects ensuring a squeezing, which is mechanical and/or byevaporation which is all the more considerable-as the speed of the flowis high. The excess of active agent is projected into the chamber 38 andreturns to the tank 40.

When the thread A has penetrated into the chamber 32, there remainsthereon a quantity of active agent, which is perfectly determined as afunction of the con.- ditions of the treatment, particularly of thespeed of the thread and the P /P, ratio. Such conditions may easily bereproduced.

When the thread A arrives near the aperture 32c, it is subjected outsidethe divergent part to a decompression provoking the evaporation of theliquid which it is carrying. This is due, as has been seen, to theformation of a network of stationary shock waves, on condition that theratio P /P is suitable and higher than the critical value which iseasily calculated as a function of the dimensions of theconvergent-divergent nozzle 32c. After the instantaneous evaporation ofthe liquid, only the dye remains on the thread.

In other words, the passage of the thread in the aperture 32b enablesthe dosage of the final dye to be determined, whilst its passage in thedecompression zone located at the outlet of the aperture 32 enables itsquantity of humidity to be considerably reduced without modifying thequantity of dye which is applied thereto.

The thread may then be subjected to dye-fixing, drying or othertreatments.

It is obvious that as a function of the more or less dark shades whichit is desired to obtain, a plurality of apparatus such as that one whichhas just been described may be disposed one after the other.

Such an apparatus may on the other hand be slightly modified, accordingto a first variant embodiment (FIG. 4), in order that the treatment of athread, for example its dyeing according to a determined color, belimited to certain zones of the thread.

To this end, the pipe 32a is provided with an auxiliary conduit 33capable of being placed in communication with a source of compressedair, the pressure P of which is notably higher than that of the airconveyed by the pipe 32a. The Figure simply shows the conduit 34carrying this compressed air at high pressure.

,Means which have generally been designated by reference 35 enable theconduits 34 and 33 to be connected or on the contrary the air carriedthrough conduit 34 to be directed towards the atmosphere through conduit36, whilst isolating conduit 33. Various types of valves may be used,but it seems judicious to provide a fluid controlled binary triggercircuit shown schematically in FIG. 3 and comprising two control pipes37, 37a. It is known that by means of a current of gas guided throughpipe 37 or through pipe 37a, the main flow, which must then besupersonic, may be directed either towards the conduit 33 or towards theconduit 36 from conduit 34.

The operation is then as follows:

The pressure-P in the pipe 32a is firstly regulated so that it is higherthan the critical pressure in the nozzle 32c but lower than the criticalpressure in nozzle 32b. This latter characteristic may be obtained bysuitably adjusting, in known manner, the pressure P prevailing in thechamber 38, moreover taking into account the shape of the nozzle 32b.

Similarly, the pressure P is regulated so that it is higher than thecritical pressure in the nozzle 32b this pressure P,, is thennecessarily higher than the critical pressure in the nozzle 32c.

When the compressed air at high pressure P carried by the conduit 34 isdirected towards the chamber 32 throughconduit 33, the operation isidentical to that which was described hereinabove with reference to FIG.3 the thread brings inside the chamber 32 a dosed quantity of activeliquid and is squeezed at the outlet of the aperture 32c.

If the air coming from conduit 34 is directed towards the atmosphere,the pressure reduces sharply in the chamber 32 and becomes lower thanthe critical pressure in the nozzle 32b. The flow through this nozzletherefrom becomes of the turbulent type. There is therefore no longerany evaporation before the nozzle 32b but solely a mechanical squeezingsimilar to atomization. v

However, it is ascertained that this squeezing becomes very violent fora certain duration of time when the communication is re-establishedbetween the conduit 34 and the chamber 32. During this transitoryperiod, during which the pressure in the chamber 32 tends to becomeagain higher than the critical pressure at 32b, all the liquid carriedby the thread is expelled therefrom, including the dye, before thethread penetrates into the chamber 32. It seems that this phenomenon maybe explained by the fact that, as the speed of the air is always sonicat the constriction of the nozzle 32c, the waves of turbulence whichmove in the chamber 32 at sonic speed reflect on the barrier constitutedat the constriction of 320 by the front of the supersonic flow in thisnozzle 320. The waves reflected at 32c move towards 32b and the energythat they convey is added to the energy normally dissipated in thenozzle 32b. Whatever the exact explanation of the phenomenon, it isascertained that before entering into the chamber 32, the thread is in apractically identical state to that which it had when it entered inchamber 31 (FIG. 3).

The duration of this phenomenon is however limited it depends of courseon the respective values of P and P as well as on the volume constitutedby the chamber 32 and the conduit 33. This phenomenon disappears howeveras soon as the equilibrium is reached and the pressure P prevails in thechamber 32 and an operation similar to that of FIG. 3 is had again.

It is easily understood that a judicious succession of the two phases ofoperation enables portions of treated thread to be obtained whichalternate with portions of nontreated thread.

These non-treated portions may then receive a different treatment, forexample another dyeing, in a consecutive apparatus similar to that whichhas just been described. To this end, it will be judicious to ensure acoupling between the controls of the two fluid-controlled binary triggercircuits in order to obtain the regularity of the two successivetreatments.

According to a second variant embodiment which may be seen in FIG. 5,the conduit 33 may be equipped with a generator 39 of sonic orsupersonic vibrations. The operation is similar to that described withreference to FIG. 4 on condition that the conditions are such that theratio P /P is close to the critical ratio permitting the appearance ofthe shock waves near the aperture 32b, whilst being lower than thiscritical ratio.

When the generator 39 is started, a concentration of energy isascertained, as in the preceding case, near the aperture 32b, ensuringthe complete squeezing of the thread before it enters in the chamber 32.

Of course, there again, a plurality of consecutive apparatus may beprovided for effecting different treatments on consecutive portions ofthe thread, thanks to a suitable coupling of the vibration generators.

According to a third variant embodiment shown in FIG. 6, the conditionsof flow near the nozzle 32b may be modified by modifying only thepressure P in the chamber 38 whilst maintaining the pressure P in thechamber 32 constant. As may be seen, a vibrating reed whistle 39a hasbeen disposed on the wall of the chamber 38. When the vibrating reedobturates the evacuation aperture of the whistle, the pressure P increases so that the ratio P /P reduces and becomes lower than thecritical value. On the contrary, when the vibrating reed uncovers saidevacuation aperture of the whistle, the conditions of flow in the nozzle32b tend towards the critical conditions provoking, in a manner similarto that explained hereinabove, a concentration of energy near 32b and acomplete squeezing of the thread before it enters in chamber 32.

It should be noted that in this case, the vibration frequency of thewhistle will be regulated as a function of the speed of the thread inorder to obtain suitable lengths of treated thread and non-treatedthread.

Of course, the invention is not limited to the embodiments that havejust been described, but covers on the contrary all the variantsthereto. In fact, it is an easy matter to conceive that the number,succession and dimensions of the various treatment and recovery chamberswill have to be adapted to the characteristics of the elementary phasesof a complex treatment, as well as to the nature of the thread to betreated. In particular, the succession without interruption of treatmentchambers by active fluids may be envisaged, these latter being eitherliquid or gaseous or even constituted by suspensions of solid particlesin liquids or gases.

What we claim is:

1. Process for the continuous treatment of a thread during therectilinear displacement thereof which comprises:

passing said thread through a first treatment zone to subject saidthread to a treatment liquid;

passing said thread through a recovery zone to recover excess treatmentliquid; and

passing said thread through at least one convergentdivergent fluidnozzle while supplying gas to said nozzle at a pressure at least asgreat as the critical pressure of said nozzle thereby subjecting saidthread to subsonic gaseous flow in the convergent part of said nozzle,supersonic gaseous flow in the divergent part of said nozzle and anetwork of shock waves located outside of the divergent part of saidnozzle whereby said treatment liquid is evaporated from said thread.

2. Process according to claim 1 which includes the further steps ofpassing said thread through an additional plurality of seriallyconnected treatment zones, recovery zones and convergent-divergentnozzles.

3. Process according to claim 1 wherein said step of supplying gas tosaid nozzle is regulated as a function of the desired quantity ofresidual humidity in the zone following said convergent-divergentnozzle.

4. Process for the continuous treatment of a thread during therectilinear displacement thereof to produce treated and non-treatedzones which comprises:

passing said thread through a treatment zone to subject said thread to atreatment liquid;

passing said thread through a recovery zone to recover excess treatmentliquid;

passing said thread through first and second convergent-divergent fluidnozzles;

supplying gas to said second nozzle at a pressure at least as great asthe critical pressure of said nozzle; and

supplying gas to said first nozzle at pressures alternately higher andlower than the critical pressure thereof whereby said second nozzlecontinuously dries said thread and said first nozzle dr ie s said threadwhen supplied with gas above its critical pressure but expells saidtreatment liquid when supplied with gas below its critical pressure.

5. Process according to claim 4 wherein said step of supplying gas tosaid first nozzle at pressures alternately higher and lower than thecritical pressure thereof is accomplished by supplying said gas at aconstant pressure and intermittently generating sonic or supersonicvibrations in said gas.

6. Process according to claim 4 wherein said step of supplying gas tosaid first nozzle at pressures alternately higher and lower than thecritical pressure thereof is accomplished by supplying said gas atconstant pressure and alternately modifying the ambient pressure outsideof said nozzle.

2. Process according to claim 1 which includes the further steps ofpassing said thread through an additional plurality of seriallyconnected treatment zones, recovery zones and convergent-divergentnozzles.
 3. Process according to claim 1 wherein said step of supplyinggas to said nozzle is regulated as a function of the desired quantity ofresidual humidity in the zone following said convergent-divergentnozzle.
 4. Process for the continuous treatment of a thread during therectilinear displacement thereof to produce treated and non-treatedzones which comprises: passing said thread through a treatment zone tosubject said thread to a treatment liquid; passing said thread through arecovery zone to recover excess treatment liquid; passing said threadthrough first and second convergent-divergent fluid nozzles; supplyinggas to said second nozzle at a pressure at least as great as thecritical pressure of said nozzle; and supplying gas to said first nozzleat pressures alternately higher and lower than the critical pressurethereof whereby said second nozzle continuously dries said thread andsaid first nozzle dries said thread when supplied with gas above itscritical pressure but expells said treatment liquid when supplied withgas below its critical pressure.
 5. Process according to claim 4 whereinsaid step of supplying gas to said first nozzle at pressures alternatelyhigher and lower than the critical pressure thereof is accomplished bysupplying said gas at a constant pressure and intermittently generatingsonic or supersonic vibrations in said gas.
 6. Process according toclaim 4 wherein said step of supplying gas to said first nozzle atpressures alternately higher and lower than the critical pressurethereof is accomplished by supplying said gas at constanT pressure andalternately modifying the ambient pressure outside of said nozzle.